Ever since Edward Snowden opened his files, fears about overreach in the American security establishment have focused on the risk of government snooping in an age when so much of our personal lives can be divined from internet data clouds. Sections of the American public, egged on by the liberal and libertarian fringes, now convince themselves that they live on the cusp of a dystopian surveillance-state where at any moment, the wrong kind of president can turn the US into what Snowden called a “turnkey tyranny”. Much of this fear is based on hypotheticals, not reality. The Snowden files have never revealed an actual incident of abuse and the combination of an independent judiciary, Congressional oversight and a vibrant free media puts plenty of hurdles in the way of any would-be tyrant US president.

There is, however, something that civil libertarians really should be worried about. Something that is not hypothetical, but real — a truly gross overreach that actually happened in the recent past and the full extent of which is still being covered up. The first steps to rectifying this could take place as early as this week, if the US Senate’s intelligence committee votes to declassify a 6,300-page report on the CIA’s use of enhanced interrogation (torture, by United Nations and most other definitions) in the years after September 11.

Based on what has been made public so far, at least 136 individuals were subjected to this barbarity, aided and abetted by 54 foreign governments, including Britain, which has never officially admitted its role, but in 2012 was forced to pay a £2.2 million (Dh13.32 million) settlement to a Libyan dissident who was sent to Tripoli for torture. This Senate torture report, which Barack Obama says he wants declassified, is the distillation of six million documents. They tell the full story of an episode for which there has never been a proper reckoning — not in the White House, not in the courts and not with the publics of Britain or America. The CIA has done its best to frustrate the process, infamously destroying video tapes of the “enhanced interrogations” in 2005 and now, through redactions and revisions, delaying the declassification that was first approved by the intelligence committee more than a year ago.

In the latest row, Dianne Feinstein, the intelligence committee chairman, took to the floor of the Senate to accuse the CIA of snooping on her staff’s computers after discovering that it had inadvertently handed over an embarrassing document. Obama signed an executive order banning torture two days after taking office, but, for practical reasons, he gave those involved a free pass by failing to hold to account those responsible. Now he covers himself by expressing support for the release of the report “so that the American people can understand what happened in the past”. But he also does nothing to hasten the process of full disclosure. Sincere or not, Obama is right.

The American and British people do need to understand what happened in those black jails and — even more importantly — to appreciate what was given away when their governments stooped to torture. When Vladimir Putin mocks the West over its selective love of international law, when the Chinese refuse to take lectures over the torture of their dissidents, it is partly this shameful episode with which they scorn the West. America can retort (truthfully) that democracies admit their mistakes and clean house while autocracies deny and cover up — but even that defence is denied to America if this report gets buried. It must be published even though, as those who have read it are hinting, it will make deeply uncomfortable reading and reveal shocking new information about the scale of the torture programme.

Republicans want to protect the reputation of George W Bush, the CIA wants to protect its officers from prosecution and even the Obama White House — with its devotion to drone strikes and National Security Agency data mining — has reasons not to want to dwell on the past. But all these special interests must be overcome. If it unlocks the door, then perhaps, reluctantly, a legal amnesty should be granted to kick-start the truth and reconciliation process — because it is clear that the American and British public have never confronted what was done in their name.

One small illustration of this was the most shamefully under-reported story of the 2012 US general election, in which a leaked memo showed Mitt Romney’s advisers urging him to “rescind and replace” Obama’s 2009 executive order banning torture and reintroduce “enhanced interrogation”.

Given Romney’s previous statement saying that he did not believe waterboarding to be torture, in a 2008 televised campaign debate with the resolutely anti-torture John McCain, it is not unreasonable to assume he might have taken that advice. America should have erupted with indignation. Instead, what should have wrecked the Romney campaign passed almost unnoticed. There is still nothing to stop a new president rescinding Obama’s anti-torture order, which is why public opinion — too often glibly supportive of torturing terrorists — needs to be acquainted with the facts in all their gruesome detail. Those who complain that the intelligence community is “drunk with power, unrepentant and uninclined to relinquish power” — to quote a speech by Senator Rand Paul last week — should be camped on the steps of the Capitol, demanding nothing less.

— TheTelegraph Group, Limited, London, 2014